Since synonyms are created automatically when renaming a page, and the synonym uses the old title of the page, it is important to preserve a user who bears some responsibility for the wording of that title for moderation purposes.
If the person who renames the page is credited with the old title and the page was renamed because it contained bad words or something, then the wrong user might get a warning or reprimanded for the synonym even though they were not the one who chose it.
Since the user is being credited in activity, we will back-date the synonym to the creation time of the page to prevent it from appearing there. In a future version when we make some changes to history storage we can get more specific and attempt to use the last time the page was renamed, or we can flag certain synonyms as auto-generated and to ignore those in activity (since they would be a duplicate of the activity for the rename-action).
However, this actually has nothing to do with the bug report you referenced on your site, which is about a category that was created. The category was generated automatically based on the current content of the page at the time of import, when the credited user was the last person who edited it (they were credited using the last edit time of the related edit). I notice that this is in conflict with a
previous description of importer spec that was provided to you, so this conflict has been corrected to use the importer-runner in future imports in the next release.
I should note that the importer does not automatically generate synonyms based on detected renames, so this issue was not related to synonyms either.
Regarding the image files, this seems to be related to having wiki-attachment history disabled, and I'm guessing you updated content-tags on the files at that time. It looks like if a wiki-attachment is modified outside of the standard wiki editor, it was incorrectly trying to generate a new upload for the attachment even though no upload was made. Aside from the date getting bumped, this appears to be relatively harmless. It should be fixed in the next release by double-checking that an upload was actually made before bumping the date.